﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Security.Cryptography;

namespace CrypHelper
{
    public class DiyCrypto
    {
        private SymmetricAlgorithm mobjCryptoService;
        private string Key;
        /// <summary>  
        /// 对称加密类的构造函数  
        /// </summary>  
        public DiyCrypto()
        {
            mobjCryptoService = new RijndaelManaged();
            Key = "IQONDA-1QWQ13MD8SS712-CHRI4EE255-FFQ-232RF121";
 
        }
        /// <summary>  
        /// 获得密钥  
        /// </summary>  
        /// <returns>密钥</returns>  
        private byte[] GetLegalKey()
        {
            string sTemp = Key;
            mobjCryptoService.GenerateKey();
            byte[] bytTemp = mobjCryptoService.Key;
            int KeyLength = bytTemp.Length;
            if (sTemp.Length > KeyLength)
                sTemp = sTemp.Substring(0, KeyLength);
            else if (sTemp.Length < KeyLength)
                sTemp = sTemp.PadRight(KeyLength, ' ');
            return ASCIIEncoding.ASCII.GetBytes(sTemp);
        }
        /// <summary>  
        /// 获得初始向量IV  
        /// </summary>  
        /// <returns>初试向量IV</returns>  
        private byte[] GetLegalIV()
        {
            string sTemp = "ZXCADSQEW123DPIU1D7-12NMD912-FM52-DAR51-1";
            mobjCryptoService.GenerateIV();
            byte[] bytTemp = mobjCryptoService.IV;
            int IVLength = bytTemp.Length;
            if (sTemp.Length > IVLength)
                sTemp = sTemp.Substring(0, IVLength);
            else if (sTemp.Length < IVLength)
                sTemp = sTemp.PadRight(IVLength, ' ');
            return ASCIIEncoding.ASCII.GetBytes(sTemp);
        }
        /// <summary>  
        /// 加密方法  
        /// </summary>  
        /// <param name="Source">待加密的串</param>  
        /// <returns>经过加密的串</returns>  
        public string Encrypto(string Source)
        {
            byte[] bytIn = UTF8Encoding.UTF8.GetBytes(Source);
            MemoryStream ms = new MemoryStream();
            mobjCryptoService.Key = GetLegalKey();
            mobjCryptoService.IV = GetLegalIV();
            ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
            cs.Write(bytIn, 0, bytIn.Length);
            cs.FlushFinalBlock();
            ms.Close();
            byte[] bytOut = ms.ToArray();
            return Convert.ToBase64String(bytOut);
        }
        /// <summary>  
        /// 解密方法  
        /// </summary>  
        /// <param name="Source">待解密的串</param>  
        /// <returns>经过解密的串，返回空则表示错误的加密串</returns>  
        public string Decrypto(string Source)
        {
            string truecode = null;
            try
            {
             byte[] bytIn = Convert.FromBase64String(Source);
            MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length);
            mobjCryptoService.Key = GetLegalKey();
            mobjCryptoService.IV = GetLegalIV();
            ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
            StreamReader sr = new StreamReader(cs);
          
            
                  truecode = sr.ReadToEnd();
            }
            catch (Exception)
            {
                  truecode = null;
            }

            return truecode;
        }
    }
}
